Very high capacity boxing machine



A. A. E. SEVAL VERY HIGH CAPACITY BOXING MACHINE Jan. 19, 1960 Filed March 2a, 1958 5 Sheets-Sheet 1 Emu. (.QaTJccS Jan. 19, 1960 'A. A. E. SEVAL 2,921,425 I VERY HIGH CAPACITY BOXING MACHINE Filed March 28. 1958 5 sheets-sheet 2 MM 6am Jmg Jan. 19, 1960 A. A. E. sEvAL 2,921,425

vERy HIGH CAPACITY BOXING MACHINE 5 Sheets-Sheet 3 Filed March 28, 1958 ERR! Loans fif/i/rpea Jamie, 1960 A, A, E, SEVAL 2,921,425

VERY HIGH CAPACITY BOXING MACHINE Filed March 28', 1958 5 Sheets-Sheet 4 Jan. 19, 1960 A. A. E. SEVAL 2,921,425

v VERY HIGH CAPACITY BOXING MACHINE Filed March 28, 1958 5 Sheets-Sheet 5 MM W/ United States Patent VERY HIGH CAPACITY BOXING MACHINE Andr Amand Etienne Seval, Rue Neuve, Vergeze, France Application March 28, 1958, Serial No. 724,532

Claims priority, application France April 4, 1957 i 4 Claims. (Cl. 53-247 The present invention relates toa very high capacity machine for automatically boxing any articles capable of being picked-up by grippers.

For the sake of simplicity and clearness, the specification will refer to bottles only, but it is to be understood that this is but a mere example of the use of the machine, without any intention of limiting the invention.

The apparatus consists of two superposed conveyors, the upper one conveying the bottles and the lower one bringing the boxes. Both of these are located in a vertical plane and are advancing in the same direction.

The upper conveyor ends abruptly; at its free end, it is connected to the lower conveyor by means of a carrier having multiple gripper-heads, said heads being swingingly mounted between two parallel driving chains.

This carrier is inclined and the heads pick up the bottles at the free end of the upper conveyor and deposit them in the boxes which are advancing below on the lower conveyor. Bottles must circulate and be placed in an upright position. The machine also comprises a bottle-selector and a box-selector.

On the most advantageous side of the machine (right or left), a motor unit provides for the drive thereof; this drive is transmitted to the various members by roller-chains; all members are protected by safety devices.

Other advantages and features of this invention will become clear on reading the following description with reference to the accompanying drawings, in which:

Figure l is a general diagrammatic side elevation of the machine according to the invention;

Fig. 2 is a diagrammatic plan view of the bottleselector;

Figure 3 is a partial diagrammatic plan view of the box-selector;

Figmre 4 is a partial enlarged plan view of a gripperhead, only one roller with its chain being shown;

Figure 5 is an end-view of a gripper-head, the supporting shaft being cut-oir", so as to show the control-means for closing the bolts;

Figure 6 is a side elevation of a gripper-head, the roller being shown in mixed lines;

Figure 7 is a detail view of a bolt;

Figure 8 is a side view of the same bolt;

- Figure 9 is a sectional view of this bolt along the line X-X; and

Figure 10 is a general electric wiring diagram of the drive control and of the safety-device circuit.

The main components of the machine according to the present invention are:

(A) The frame;

(B) The gripper-heads;

(C) The carrier provided with swinging hook elements (hereafter referred to as carrier);

(D) The bottle-selector;

(E) The bottle-conveyor;

(F) The box-selector;

(G) The box-conveyor;

(H) The motor-unit.

(A) The frame is essentially formed of U and L- shaped irons, assembled partly by welding and partly by bolts.

At its lower portion, two beams 1 support the boxconveyor 2 and its selector 3; at the upper portion, two other beams 4 support the bottle-conveyor 5 and its selector 6 (Fig. 2) as well as its end-able 7. The return and driving spindles are mounted on these beams. At the rear portion (upstream side of the movement), two vertical legs 8 connect these four beams to one another. They do not extend beyond the upper conveyor.

At the front portion (downstream side of the movement) two standards. 9 also connect these four beams, but they carry, besides, at their tops the upper extremity of the carrier 10, the driving members and the lateral flanges 48a. At their lower portions, these side flanges are connected to the lower beams; they form the sides of the carrier and support various fittings.

The carrier-assembly 10 is enclosed in a casing 56, made of a plastic material, the sides and the top thereof being removable. The beams and legs are transversely braced by suitable horizontal cross-bars.

(B) The gripper-heads P are rectangularly shaped plates, consisting of stainless steel plate-members 13, 14 and 15 (Figures 5 and 6) separated by spacer-plates 16 and 17 made of plastic material. The width and the length of the rectangular plates are slightly smaller than the inner dimensions of the corresponding boxes; their thickness depends on the kind of articles to be grasped.

The lower portion of each rectangular plate comprises groove-shaped recesses 18, the number of which corresponds to that of the rows of bottles to be boxed (here again, for the sake of clearness, the number of bottles to be picked up will be kept to 15, in three S-bottle rows). The head will then have three grooves 18 (Figure 5). The size of these grooves will be adequate to accommodate the neck of a corked or uncorked bottle, with the normal clearance required to avoid shocks. Similarly, the depth is so designed as to allow for a margin in case all sets of bottles are not of absolutely like height.

In the side-walls of these grooves are located halfbolts 19 (Figure 7 and following), also made of a plastic material.

In their open position, these bolts do not protrude into the grooves. When being closed, they leave their housings and take up positions under the bulging portion provided on the bottle-neck, on either side thereof. These bolts comprise a body-portion 19, an L-shaped gripperportion 20 pivotally mounted in the body-portion 19 and free to move about a pin 21. This movement of the gripper 20 is forwardly limited by a stop 22 and rearwardly by a leaf-spring 23. This movement, which has a very small amplitude, enables the bottles of the same row to be correctly gripped, even if there is a slight difference between the diameters of the necks.

The horizontal wing of the L has a semi-circular shape, in the horizontal plane thereof.

These half-bolts are secured to the tie-bars 24 and 25, each of the latter carrying the half-bolts in the same direction. The assembly is effected by means of tenons 26 and screws 27. The tie-bar-half-bolt assembly can slide horizontally through the corresponding openings provided in the plates 13 and 14.

On the upper plate 13 of the head are screwed, by means of screws 29 extending through the whole assembly, two bearings 28 through which passes apin 30 journalled in these bearingsand carrying at either end a roller 31. The free ends of the pin 30 are screwthreaded. They extend into an opening provided therefor in a special link 32 of the driver chains 33 (Figure 1). The journals and rollers are hushed with sintered bronze to render their lubrication unnecessary. The pin 30 is limited in its lateral movement by means of twoadjusting rings 34.

Still on this plate 13 and longitudinally located, a spindle 35 provides for the opening and the closing of the bolts. For this purpose this spindle 35 extends through each of the bars 24 and 25, through an opening provided in each of the latter, and comprising a housing 36, located in the lower portion for one kind of bars and in the upper portion for the others. Lugs 37 are engaged in this housing, said lugs being keyed to the spindle 35 and in a diametrically opposite relationship. Thus, by causing the rotation'o-f the spindle 35, the lugs will cause the bars to move forwards or backwards, thus providing for the opening or the closing of the bolts.

This rotation is transmitted to the spindle 35 through the medium of a link arrangement 38 and 139, these links being in turn controlled by a closing arm 40, at the extremity of which is located the roller 41, said roller being adapted to bear against a control rail 4-2 (Figure l). The closing arm 40 is guided during its vertical movement by a pivot-pin 43, keyed, on the one hand, to the plate 13, and held, on the other hand in its upper part,

by means of a support 44 (Figure 4). The vertical stroke thereof, drives, by way of the spring 45, the sliding member 46, which carries the links 39 laterally. In this Way, the closing of the bolts has always a maximum efliciency, spring 45 providing for such complete closing, even .if the arm 40 takes up a slightly toolow or slightly too high position.

The opening of the bolts is effected by means of a return spring 47, when the arm 40 is freed from the constraint of the rail 42.

The link 38 has also the spindle 35 passing therethrough, to which it is keyed. The link 38 .is also adapted to hold this spindle 35 in its accurate longitudinal position, by coming to bear slightly on the central bar 24, whereas the bar 25 does the same in the other direction, by means of a stop ring 48.

(C) The carrierfprovided with swingingly mounted heads is formed of two flanges 48a made of sheet material and shaped as corner-irons (Figure 1).

Seen edgewise, it is shaped as an obtuse angle, the apex of which is directed upwardly, one of the sides being almost parallel to the upper conveyor, the other one being at an angle of about 45 in relation to said upper-conveyor.

On each flange, and placed opposite one another, are located slope-changing return pinions. They are mounted in an overhang relationship to the flanges, as the space between said two flanges is necessarily left free to allow the heads to pass. They cannot therefore be connected by cross-bars, but the upper portions of the flanges are connected by braces.

Looking at the machine as shown in Fig. 1, the lower part of the carrier is on the left. The pinions are placed as follows: at the left bottom two return pinions 49, 50; at the upper corner, one slope-changing and tensioning pinion 51; below, another slope-changing pinion 52; at the right end, a large return-and-control pinion 53.

The chain 33, on either side, bears on this pinionassembly. This steel-linked chain is provided at predetermined locations with special links, some of which are designed to carry the swinging hook elements, the others being provided with catches and intended for vari ous controls.

The links 32 (Figures 4 and carrying the swinging hooks, thus ensure the connection with the heads forming the swinging elevating device.

The number of the heads varies in accordance with the desired output of the machine.

Inside the flanges, are secured two rails 54 on which the rollers 31 of the gripper-heads can roll. They are interrupted and offset at both ends of the circuit, so as to be always beneath the rollers. A third rail 42 located in an intermediate position between the rails 54, controls the closing of the head-bolts.

In addition, the flanges carry safety devices or auxiliary controls. Amongst these, at the upper rear side of the control pinions 53, these flanges carry the articulations of a rake 55, which is a kind of articulated strap used to gather and to put the bottles into the circuit, as will appear from the description of the operation of the machine.

As has already been said, the carrier supports the plastic casing 56.

(D and E) Bottle-selector and bottle-conveyor. These two parts of the machine, being closely inter-connected, will be described together.

The selector and the conveyor are formed of bladeprovided chains, of normal or special pitch, according to requirements.

In the direction of movement, this assembly is divided into three parts.

In the first place, in the rear part, input chains 57 (Fig. 2) are spaced by an interval 58 which is equal to one of the chains.

In the second place, all chains are contiguous, thus forming a travelling-band.

In the third place, in the front part and beyond the pinion 59 for the return of the chains, there is a smooth table 7, made of stainless steel.

In the rear part, the chains are spaced. Their number is equal to that of the bottom-rows (e.g., in the case of 15 bottles: three chains 57 and two intervals 58). These intervals allow the articulations of the selector, the safety devices and the shielding-members to be placed on the lateral flanges.

At the rear of the selector, at the machine inlet, are located conveyors 60 of a known type, which are connected to the selector proper by means of a very short bridge 61.

In the direction of movement, the bottles pass over a first set of retractable stops 62, and in accordance with the number of bottles provided for each row, through a plurality of doors 63. Beyond these, the shielding members '64 (Figure 2) of the outer rows are returned to the center, thus grouping the three bottle-rows on the travelling-band, formed at the central portion of the upper conveyor.

The doors 63 and the stops 62 are controlled by a rod-linkage, placed under the conveyor 65, and the movement of which is caused by the carrier chains actuating a catch 66, by way of the arms 11, pivoting about a pivot-pin 12. The reverse movements are achieved by return springs 67.

(F and G) Box-selector and box-conveyor. As was the case for D and E, these two assemblies, being closely interrelated, will be described together.

Carried as already stated, by the lower beams 1, the rear portion of the selector consists in driven steel-"rollers 68, followed by three rollers 69, which are also driven but have a rubber sheathing.

On either side of the selector, are located shieldingmembers and also two flat members 7% pivoting centrally in the horizontal plane. These two flat-members, seen in plan-view roughly constitute a pair of scissors. The forward extremity of the branches is slightly bent inwardly (hooks 71) and the rear-part carries a blade '72 provided with prongs. The two scissors-branches are coupled and can be opened or closed by means of a rod-linkage 73, located beneath the selector. A control rod '74, followed by a swingle-bar 75 and by two lateral chain runners '76 complete the control arrangement. The chain runners engage into catches carried by the conveyor chains 77, which drive the Whole assembly, thus causing the scissors to open. The runners are freed n-nder the action of the inclined surfaces 78 and the whole assembly is brought back to its closed position, under the action of the return-springs 79 and 80.

Upstream of the selector, is placed a free roller-com veyor 81 of any known type, and which is not part of the machine according to the invention.

Downstream, the conveyor is placed in a plane which is slightly below and inclined in the direction of advancement. Between the last driven roller 69 and the inlet of the conveyor, there is provided an interval 82 for the passage of the driving bars 83 of this conveyor. The latter is formed of two chains 84, similar to those of the carrier, which are connected by means of driving bars '83, the metal portions 85 of which are adjustable.

L shaped shielding members are provided on either side. A box-positioning leaf spring 86 is placed on one side.

The bottom of the conveyor is formed by a steel sheet 87, on the front part thereof. This sheet is substantially parallel to the ground.

The chains 84 pass over pinions similar to those of the carrier.

Three pinion-sets are placed on the sides. The rearset 88' acts as a drive and a return member; the front set 89 acts as tensioning and return member; the intermediate set 90 is intended for the change of slope of the upper run of the chain. This conveyor, beyond the return pinion 89, is followed by a roller-carrier 91 of any known type.

(H) Motor unit: All frictional and rotary elements are mounted on sintered bronze rings, of the self-lubrieating type, whereby the need of lubricating is completely eliminated.

A spindle 92, placed under the table perpendicularly to the direction of advancement, carries at the most convenient end for the user (according to the available space) a pinion 93, intended for the general control. At its other end, it carries three pinions 94, 95 and 96.

These three pinions respectively control: the first one (pinion 53) the carrier return pinion; the second one (pinion 59) the movement of the bottle-conveyor chains; the last one (pinion 88) the box-conveyor chains.

The box-conveyor in its turn actuates the driven rollers of the selector. All connections are achieved by roller chains and tensioning jockey-wheels or loose pulleys.

The general driving pinion 93 is connected to the output pinion of the reduction gear of the motor unit. This unit consists of an assembly comprising: the motor, the reduction gear, the variator, the coupling gear and the limitator. This unit is electrically connected to the power source by means of a make-and-break switch 97 (Figure The electrical feeding circuit co-operates with a plurality of safety devices. The circuit of these devices is fed with 24 v. through a conventional transformer 102.

(1") As there must be no voids in the boxing, the assembly is adapted to operate only when the bottleselector is filled.

For this purpose, every bottle placed in the selector between two doors, must presson a strip, actuating a microcontact and closing the circuit. All these strips 98 are mounted in series. Therefore, should even only one bottle be missing from the circuit, the operation of the whole assembly would be stopped. This circuit feeds an electro-magnet-ic contact-finger 99, placed under the casing of the carrier near the return pinion 53; this contactfinger actuates a safety device 100 controlling the general contactor; the latter is retracted only if the microcontact circuit is closed.

(2) When bottles are being placed into the boxes, two safety devices may come into operation.

The first one 101 provides for the right location of the box. Should the latter be wrongly placed, the set of bottles will abut against the front or rear edge of the box; the head, put out of equilibrium, will take any inclined position. The head, when lowered, passes between two alarm contacts 103; these allow for the lowering of the boxes but prevent their naising. If the head is put out of equilibrium, one of the alarm contacts is urged upwards, and then actuates the safety device 101.

The second safety device provides for the supply of a box; if the box-conveyor is empty, the machine is stopped. A micro-contact 104, located behind the positioning spring 86 retracts a safety device 105 located slightly in front of the exact loading position of a box; if no box is supplied, this safety device cuts off the current.

Finally, if an excessive stress is borne by the carrier, the limitator is actuated.

In order to enable the machine to operate when unloaded, a special contactor 106 puts all safety devices out of circuit, thus enabling the motor to be started.

The machine operates as follows: the operational cycle comprises the bottle-input stage into the selector of the upper conveyor, until a box is filled.

In all boxing machines, this operational cycle is divided in several stages:

(1) Bottle-input;

(2) Rate-selection;

(3) Bottle-gripping; (4) Bottle-transport; (5) Placing into boxes.

Meanwhile, boxes arrive, are placed in position, are filled and move away.

As a single member provides for the gripping, there are compulsorily some idle moments corresponding to the return into starting position of the gripper member, or to the closing of a trap-door or to the filling of a special compartment.

In order to increase the output, either the cycle must be considerably speeded up, or the number of boxes filled simultaneously must be increased, all these operations usually being detrimental to the bottles.

In the machine according to the invention, the cycle is perfectly continuous. The heads can be placed as close as possible to each other, that is, with spacings hardly exceeding the length of box.

Assuming, for example, that 70 centimeters are reserved per box, the box itself being includedQand assumling that a box arrives only every other second (viz. 30 boxes per minute), the carrier will only be moved by 30x70 cm.=2l meters per minute, which is a perfectly permissible speed; and yet in the example given involving 15 bottles, the output is as high as 15 30 60=27.000

bottles per hour, for full size bottles; for quarter bottles, packed 24 per box, the output will be:

bottles per hour.

As bottles are picked up in an upright position and deposited in the same position, without being dropped,

no breakage is to be feared.

Moreover, in view of the manner bottles are gripped, the bolts bear no stress whatever while being opened or closed.

The cycle is therefore as follows: the bottles arrive on the users chains, and after having passed over the bridge 61, reach of the front part of the selector, the stops 62 being in a retracted position and the doors 63 being closed; the input stops when the selector is full and when the first bottles start abutting against the doors 63.

At that moment, actuated by the rod-linkage 65 and and by the catches 66, the stops 62 are inserted between two adjacent bottles and the doors 63 are opened. The selected amount of bottles driven by blade-chains is moved forward and reaches the table 7, where it stops between the shielding members in a balanced position of translation, the first bottles stopped on the table 7 arresting the advance of the succeeding bottles, the last bottles still being on the conveyor. (Adjustment to be achieved in accordance with the weight, the size and the number of bottles following each other.)

Then the selector is closed in reverse order: first the doors, then the retraction of the stops, and the selector is filled again.

.Duringthis operation, a head is lowered on the control pinion-53 and the bottle-necks are engaged into the grooves 18. The rake 55 is lowered together with the head and by bearing behind the bottles, it resumes the advance thereof, .until this rake reaches its vertical position leading to the closing of the head-bolts.

The arm 40 is lowered when brought into engagement with the rail 42. The extremity of the latter is adjustable and allows of obtaining said closing at the desired time.

The .rake resumes its raised position under the action of return springs. The loaded head follows the rails 54, which are slightly raised, lifting the bottle from the table. The head islowered along the rails and reaches its lowermost position.

While the aforesaid steps take place on the upper conveyor, ahnost similar ones occur on the lower conveyor.

The first box is engaged into the scissors of the boxselector, which are opened rearwardly, and abuts against the hooked portions 71, all other boxes following close to one another. The inlet control being actuated, the scissors are opened forwardly, under the action of the rod linkage driven by the chain runner 76, whereas they are closed rearwardly, thus stopping the following boxes. As the first box had been stopped as near as possible to the first sheathed roller 69, the latter grips said box and throws it onto the conveyor. There the box is gripped by the bar 83, and, driven forwardly, between a fixed shielding member and the positioning spring 86. The chain-runner frees the driving catch, by means of the inclined surface 78, and the scissors are closed. The accurate positioning of the box is ensured by adjusting the bars '85.

The filling must start as soon as the box is rocked onto the plate 87.

The box arrives in a slightly inclined position in order to facilitate the insertion of the bottles.

The head opens, since the locking arm 40 leaves the rail 42 which also ends with an adjustable portion.

The head is raised onto the return run of the chain.

The filled box moves away, and the next head, which is also loaded, is ready for the filling of the next box, and the cycle is repeated.

As the motor-variator unit controls: the various elements, with constant ratios, the actuation of the variator increases or decreases the speeds of the various members with a constant ratio.

The adjustable elements of the variator are put under lock and key, so that nobody, unless duly authorised can have a ready access thereto.

It is to be understood that the present invention has just been described by way of explanation without limitation of the same, and that any useful alterations can be made therein without going beyond its scope.

I claim:

1. A very high capacity machine for automatically boxing articles capable of being picked up by grippers, in which said articles are taken by groups formed of at least two parallel rows, each group being deposited into a box, said machine comprising a frame supporting at its lower portion a box-conveyor and a box-selector, said box- .conveyor comprising a control mechanism for said boxselector; an article-conveyor and an article-selector located above said box-conveyor; a table extending said article-conveyor; a chain carrier located above said table and provided with a plurality of spaced swinging hookelements supported by the chain of said chain-carrier, said elements being gripper-heads provided with retractable members adapted to seize the articles and which are rectangularly shaped plates consisting of two series of parallel tie-bars and of three horizontal superposed platemembers separated by spacer-plates, each of the upper two of said plate-members being provided with at least two openings, the lower portion of each of said rectangularly shaped plates being provided with at least two groove-shaped recesses, the size of which corresponds to that or the portion of the article to be seized by said gripper-heads, said retractable members being located in said groove-shaped recesses and being constituted for each row of a given group of articles by two series of halfbolts, each of said half-bolts consisting of a body-portion, an Lshaped gripper-portion pivotally mounted in said body-portion, the horizontal wing of the L being of semicircular shape, each half-bolt of one series of a given row of articles being secured to one tie-bar of one of said two series of tie-bars, each half-bolt of the other series of the same row of articles being secured to one tie-bar of the other of said two series of tie-bars and facing the first tie-bar, said two tie-bars being adapted to slide horizontally with a to-and-fro movement through said openings provided in said upper two plate-members; one hole with a lower recess and located about the middle of each tie-bar of one series of tie-bars; one hole with an upper-recess and located about the middle of each tie-bar of the other series of tie-bars; stopping devices for limiting the movement of said gripper-portion; two bearings on the uppermost of said horizontal three platemembers, a pin passing through said two bearings, rollers at both ends of said pin; two rails mounted in said carrier, said rollers being adapted to roll along said rails; means for actuating said retractable members, including one spindle extending through the holes of all of said two series of tie-bars; two series of lugs mounted on said spindle and diametrically located, one of said series of lugs being adapted to co-operate with the said lower recesses and the other series of lugs being adapted to cooperate with the said upper recesses; means for rotating said spindle, whereby each tie-bar of one series is moved in a direction opposite that of the tie-bars of the other series, thus actuating said retractable members; control mechanisms on the said chain for controlling said articleselector; a rake adapted to gather said articles under said gripper-heads; a motor-unit adapted to drive said box-conveyor, article conveyor and carrier; safety devices for the article-selector and for the box-selector, whereby the machine is abruptly stopped whenever at least one article is missing.

2. A very high capacity machine according to claim 1, wherein the means for rotating said spindle are constituted by one rail mounted in said carrier; one arm pivotally mounted in said hook-elements; a roller mounted at one end of said arm and adapted to roll along said rail; a sliding member mounted on said arm; a set of links pivotally secured, on the one hand, to said slidingmember and, on the other hand, to said spindle; a guidemember for said arm; a set of springs adapted on the one hand to urge said roller against said rail, and, on the other hand, to control the to-and-fro movement of said sliding member, whereby, whenever said roller comes into contact with said rail, said set of spring actuates said sliding member and, therefore, said links, thus causing said spindle to rotate in one direction and, consequently, provoking the erection of said half-bolts, and, whenever said roller no longer contacts said rail, said set of springs brings back said sliding member to its former position and, therefore, causes said spindle to rotate in the opposite direction, which causes said half-bolts to retract.

3. A very high capacity machine according to claim 1, wherein the article-conveyor and the article selector are constituted by three zones, a first zone formed of at least two spaced parallel travelling hands, a second zone formed of convergent travelling bands extending those of the first zone, a third zone formed of contiguous travelling bands extending those of the second zone; shielding members on both sides of each travelling band of said three zones; a set of retractable stops; 2. set of doors downstream of said set of retractable stops and distant 9 from the latter by a length equal to that of the article to be boxed; and wherein the control-mechanisms for controlling said article-selector are constituted by a rod-linkage provided under said article-conveyor and connected to said doors and stops; by at least one arm pivotally mounted and secured to said rod-linkage; by a catch connected to said arm and adapted to be actuated by the carrier-chains.

4. A very high capacity machine according to claim 1, wherein the box-conveyor and the box-selector are constituted by driven rollers; shielding members, two fiat members pivotally mounted in the horizontal plane about their centers and adapted to act as scissors; an inwardly bent hook at one extremity of each of said flat members; a blade provided with prongs at the other extremity of each of said flat members; a rod-linkage adapted to actuate said flat members; a control-rod extended by a swingle bar and two lateral chain-runners; chains adapted to drive said rollers; catches mounted on said chains and adapted to actuate said runners; inclined surfaces adapted to act upon said runners; elastic mem bers secured to said flat members; a box-positioning leafspring.

References Cited in the file of this patent UNITED STATES PATENTS 2,452,376 Holstebroe et a1. Oct. 26, 1948 2,615,289 Hickin Oct. 28, 1952 2,807,125 George Sept.'24, 1957 e 15 2,819,576 Hendricks et a1. .i Jan. 14, 1958 

